Abstract
Glucocorticoids (GCs) are potent regulators of energy metabolism. Chronic GC exposure suppresses brown adipose tissue (BAT) thermogenic capacity in mice, with evidence for a similar effect in humans. Intracellular GC levels are regulated by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) activity, which can amplify circulating GC concentrations. Therefore, 11β-HSD1 could modulate the impact of GCs on BAT function. This study investigated how 11β-HSD1 regulates the molecular architecture of BAT in the context of GC excess and aging. Circulating GC excess was induced in 11β-HSD1 knockout (KO) and wild-type mice by supplementing drinking water with 100 μg/mL corticosterone, and the effects on molecular markers of BAT function and mitochondrial activity were assessed. Brown adipocyte primary cultures were used to examine cell autonomous consequences of 11β-HSD1 deficiency. Molecular markers of BAT function were also examined in aged 11β-HSD1 KO mice to model lifetime GC exposure. BAT 11β-HSD1 expression and activity were elevated in response to GC excess and with aging. 11β-HSD1 KO BAT resisted the suppression of uncoupling protein 1 (UCP1) and mitochondrial respiratory chain subunit proteins normally imposed by GC excess. Furthermore, brown adipocytes from 11β-HSD1 KO mice had elevated basal mitochondrial function and were able to resist GC-mediated repression of activity. BAT from aged 11β-HSD1 KO mice showed elevated UCP1 protein and mitochondrial content, and a favorable profile of BAT function. These data reveal a novel mechanism in which increased 11β-HSD1 expression, in the context of GC excess and aging, impairs the molecular and metabolic function of BAT.
Highlights
Brown adipose tissue (BAT) is adapted to expend chemical energy in the form of heat, predominantly through the action of the uncoupling protein 1 (UCP1), and has important roles in whole-body energy homeostasis [1, 2]
11b-HSD1 expression can influence intracellular GC availability independently of circulating levels. 11b-HSD1 knockout (KO) mice are largely protected from the tissue-specific responses to circulating GC excess and demonstrate a critical role of the enzyme in transducing extracellular GC concentrations to intracellular signaling [22, 23]. 11b-HSD1 is expressed in brown adipocytes and, when overexpressed in vitro, induces GC-mediated BAT dysfunction [24], 11b-HSD1 knockdown in vitro or after pharmacological inhibition in vivo enhances BAT function in the face of a high-fat diet challenge [24], and 11b-HSD1 KO mice have been shown to have an elevated core body temperature, again suggesting an influence on BAT function [25, 26]
We show that 11b-HSD1 upregulation, in response to chronic GC excess and aging, increases brown adipocyte GC exposure to impair BAT function. 11b-HSD1 KO mice resist GC-mediated suppression of UCP1 protein, BAT thermogenic gene-expression programs, and have preserved mitochondrial function and activity
Summary
Mouse strain, storage, and aging Male mice (C57/BL6J) were group housed at 22°C for 10. Primary cell culture of brown adipocytes Interscapular BAT was extracted and manually digested before placement in collagenase, and incubated in a 37°C water bath for 40 minutes with 10 seconds of vortex every 5 minutes. Cell treatments Differentiated brown adipocytes were treated in DMEM/F12 serum-free media, with CORT Mouse BAT was excised and tissue samples were incubated with 100 nm of 11-DHC diluted into 1 mL of serum-free media in glass tubes. 9197, Cell Signaling Technology; Phos-CREB Ser-133: RRID AB_256044, catalog no. 9198, Cell Signaling Technology; mouse anti-b-actin: RRID AB_306371, catalog no. Respiratory output and mitochondrial stress tests were performed with BAT in supplemented XF-Assay media (25 mM glucose and 0.5 mM sodium pyruvate) at pH 7.4 and maintained for 1 hour at 37°C in 0% CO2 before Seahorse XF analysis (Agilent Technologies). Statistical analysis derived from RT-PCR data were determined using change in Ct values throughout
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
